The Americans planned to send armies against three targets: the Army of the Northwest would attack southwestern Upper Canada at the Detroit River; the Army of the center would capture central Upper Canada at the Niagara River; and the Army of the Northeast would move against Montreal. As events soon showed President James Madison and other American leaders had not made adequate preparations to fight a war.
At the beginning of the war, the Americans held a fort on Michilimackinac (which is also known as Mackinac Island), in the strait between Lake Huron and Lake Michigan. It commanded the fur routes. Traffic came from the portages from Lake Superior over Sault Ste. Marie into Lake Huron, past Mackinac. It was a post of vital strategic importance. It was 300 miles from the next nearest American post, at Detroit. The Americans failed to get word of the declaration of war to their own men. The British notified their own forces through the traders of the Northwest company and managed to capture the fort.
The Americans under Brigadier General Hull were massing an army of 2,300 men at Detroit. The British fort at Amherstburg was poorly constructed, and its garrison consisted of a few hundred regulars and some militia. Brock determined to strike first. He took a force of about 300 men from the garrisons on Lake Ontario and marched to Port Dover, on Lake Erie. They embarked in bateaux (a bateau was a flat bottomed, round sided boat, propelled by oars or poles, which could also be sailed) and any available ships and sailed for Amherstburg.
According to Berton's The Invasion of Canada the Nancy was a 100 ton schooner owned by the Northwest Company. She was one of the ships used by Brock to travel to Amherstburg. They went across, rather than around, Long Point, and had to manhandle the Nancy across.
The Nancy had been built in 1789 at Detroit. Travel between the Great Lakes was limited. It was also possible for ships to sail down the St. Clair River from Lake Huron to Lake St Clair, and down the Detroit River to Lake Erie. Lake Superior was isolated from Lake Huron by the rapids of Sault Ste Marie, and Lake Erie was isolated from Lake Ontario by the Niagara escarpment. The Nancy sailed the Erie/St Clair/Huron system for the Nor'Westers, carrying trade goods to meet the canoe brigades coming from the west
At the time, Long Point was an island. In later years, the channel between Long Point and the mainland was dredged, and then later filled in with a causeway. What Brock faced was getting the ship across a shoal or sandbar.
Brock arrived at Amherstburg, and enlisted the support of Tecumseh's loosely united First Nations. Legend has it that Tecumseh reported to his allies of Brock: "This is a man". Brock's aggressive style appealed to the First Nations leaders and their warriors.
Brock crossed the river and took Detroit without a fight. Brock's message demanding the surrender pointedly warned that Brock had no military control over his First Nations allies. Historians believe that General Hull was terrorized at the thought of an Indian massacre. With the victory, the Canadians controlled the frontier north to Mackinac Island. They fought a further battle with the Americans on the Raisin River in northern Michigan in January 1813, and won a decisive victory. However, the British were unable to restrain their native allies from killing and torturing prisoners and scalping the dead. The British victory was seen as an atrocity by the Americans, and the western states cried for revenge.
With the Western frontier secured in the summer of 1812, Brock turned his attention to the Niagara frontier, along the Niagara river at the east end of Lake Erie. The Americans were massing another army. The British defences extended from Newark, on Lake Ontario, upriver through Fort George and the village of Queenston. Above Queenston, the Niagara escarpment rose into a 300 foot ridge known as the Heights. It was impossble to cross the river above Queenston, due to the presence of the Niagara Falls.
The Army of the Northeast had not even been collected by that time. It was hoped that the Army of the Center, forming along the Niagara River, would be able to achieve a decisive victory and begin the march across Upper Canada. The army was destined to clash with the British at Queenston.